Answer
Xenophon, a Greek historian and military leader, is the primary historical source on Epaminondas' military tactics. His writings, particularly his "Hellenica," provide detailed accounts of Epaminondas' innovative strategies, such as the oblique order of battle, which he employed to great effect at the Battle of Leuctra. Xenophon's firsthand observations and analysis offer valuable insights into Epaminondas' military genius and his influence on ancient warfare.